1. Field of the Invention
The present invention relates to an article transfer method using a self-propelled carriage capable of travelling along a fixed path and holding articles, and to a self-propelled carriage.
2. Description of the Related Art
In the prior art, an article carrying vehicle as disclosed in Japanese Unexamined Patent Publication No. 10-139172 has been proposed as a device of this kind. This article carrying vehicle comprises a laterally sliding table capable of moving in lateral directions (vehicle width directions), and a longitudinally sliding table capable of moving in forward and rearward directions (longitudinal direction of a vehicle) provided on the laterally sliding table. Furthermore, a turning platform is provided on the longitudinally sliding table to be rotatable about a vertical axis, and a fork device is provided on the revolving platform to be vertically movable. Furthermore, an upper cover portion for covering articles mounted on an article transferring section is also provided on the vehicle, and shutters are provided on either side of the upper cover section in the lateral direction of the vehicle body.
When transferring an article by using an article carrying vehicle of this kind, firstly, the article carrying vehicle is caused to travel along a fixed path and is halted alongside a station, and in this state, the station side shutter is opened. Thereupon, the laterally sliding table is moved to the station side, so as to move the longitudinally sliding table, the revolving platform and the fork device in an integrated fashion. The fork device is moved upward, and then the revolving platform is turned to cause the fork device to turn to be movable in lateral directions. Thereupon, the longitudinally sliding table is moved forward or rearward, thereby correcting the longitudinal-directional position of the fork device with respect to the station.
By moving the fork device to project, and then to lower, the article is transferred to the station side. Subsequently, the fork device is retracted, and then the revolving platform is turned to cause the fork device to be in a longitudinal orientation. The laterally sliding table is moved over the vehicle body, and then the shutter is closed, thereby completing the transfer of the article to the station. As for loading an article to the article carrying vehicle, it can be performed in a similar manner but with a different timing for vertically moving the fork device.
However, according to the prior art constitution described above, the fork device, which is the final operating section, is caused to move laterally and longitudinally, and turn, with respect to the vehicle body, and in order to achieve lateral and longitudinal movement in this case, it is necessary to adopt structures respectively comprising motors, guiding means (guide rails, or the like,) base members, and the like, and hence the overall structure becomes complicated and expensive, in addition to which, the operating time (work time) becomes longer and the control tasks become more complex.